The invention relates to improved laundry detergent bars. More particularly, it relates to laundry detergent bars comprising a mixture of anionic surfactants comprising alkylbenzene sulfonate and alkyl sulfate, detergent builders, and fatty alcohol, and which are substantially free of fatty acid. The bars exhibit improved bar wear rate and smear.
Detergent compositions in the form of synthetic detergent granules and liquids are used in many societies to launder clothes, particularly in those societies where mechanical washing machines are common. In portions of such societies, and more frequently in societies where mechanical washing machines are not common, laundry detergent bars comprising synthetic organic surfactants and detergency builders are used in the laundering of clothes.
Technical developments in the field of laundry detergent bars have concerned formulating bars which are effective in cleaning clothes; which have acceptable sudsing characteristics in warm and cool water and in hard and soft water; which have acceptable in-use wear rates, hardness, durability, and feel; which have low smear; and which have a pleasing odor and appearance. U.S. Pat. No. 3,178,370 (issued to Okenfuss on Apr. 13, 1965 and incorporated herein by reference) describes laundry detergent bars comprising sodium alkylbenzene sulfonate (ABS), sodium tripolyphosphate, sodium bicarbonate, trisodium orthophosphate, and water, and processes for making these. Philippine Patent 13,778 (issued to Anderson on Sept. 23, 1980) describes synthetic detergent laundry bars containing surfactant, alkali metal pyrophosphate, from about 18% to about 60% alkaline earth metal carbonate, and from about 1% to about 20% water. Methods for making laundry detergent bars are well known in the art.
Although alkylbenzene sulfonate surfactants, such as sodium dodecylbenzene sulfonate, have been used to make satisfactory detergent laundry bars, such surfactants are derived from non-renewable petroleum-based raw materials. Accordingly, efforts have been made to formulate detergent laundry bars containing synthetic organic surfactants derived from natural sources. One such surfactant is higher fatty alkyl sulfate (AS), especially the alkali metal salt. However, use of higher fatty alkyl sulfate as a total replacement for alkylbenzene sulfonate does not produce a laundry bar with the same commercial acceptability as one made wholly from alkylbenzene sulfonate. Specifically, bars made with alkyl sulfate are more brittle and susceptible to breakage during ordinary shipment. U.S. Pat. No. 4,543,204 (issued to Gervasio on Sept. 24, 1985) discloses laundry detergent bars comprising 10 to 35% of higher fatty alkyl sulfate, and from 1 to 10% of higher fatty acid which makes the bars more resistant to breaking on handling and storage.
The consumer evaluates the performance of a laundry detergent bar against many factors, including cleaning, bar aesthetics, and the value of the detergent bar. Bar value can be diminished when the bar wears excessively during use. In use, the bar wears by abrasion of the bar while laundering the clothes and by dissolving away of the bar in the wash water. This wear can be aggravated while the bar is being stored on the wash stand between washings. On the wash stand, the bar typically lies in a puddle of water. The bar surface submerged in the water becomes gel-like as water is absorbed. This gel-like bar material wears away readily. Handling of the bar also becomes very messy.
The object of the present invention is to improve the properties of detergent bars comprising a mixture of ABS and AS by incorporating fatty alcohol into the bar. Such bars have reduced bar wear and solubility, while maintaining good cleaning and bar aesthetics.